Schedule III - Real Estate and Accumulated Depreciation - Schedule of Real Estate and Accumulated Depreciation (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	$ 948,769
Initial Cost to the Company
Land and Development Costs	334,952
Building & Improvements	1,098,783
Cost Capitalized Subsequent to Acquisition
Improvements	2,067,182
Gross Amount at which Carried
Land and Development Costs	344,409
Buildings & Improvements	3,156,508
Total	3,500,917	$ 3,133,966	$ 3,109,433	$ 2,884,486
Accumulated Depreciation	1,072,938	$ 941,612	$ 862,534	$ 747,304
111 West 33rd Street, New York, NY | office/ retail
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to the Company
Land and Development Costs	13,630
Building & Improvements	244,461
Cost Capitalized Subsequent to Acquisition
Improvements	128,857
Gross Amount at which Carried
Land and Development Costs	13,630
Buildings & Improvements	373,318
Total	386,948
Accumulated Depreciation	86,606
1400 Broadway | office/ retail
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to the Company
Land and Development Costs	0
Building & Improvements	96,338
Cost Capitalized Subsequent to Acquisition
Improvements	94,057
Gross Amount at which Carried
Land and Development Costs	0
Buildings & Improvements	190,395
Total	190,395
Accumulated Depreciation	57,716
1333 Broadway, New York, NY | office/ retail
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	158,760
Initial Cost to the Company
Land and Development Costs	91,435
Building & Improvements	120,190
Cost Capitalized Subsequent to Acquisition
Improvements	13,534
Gross Amount at which Carried
Land and Development Costs	91,435
Buildings & Improvements	133,724
Total	225,159
Accumulated Depreciation	34,132
1350 Broadway, New York, NY | office/ retail
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to the Company
Land and Development Costs	0
Building & Improvements	102,518
Cost Capitalized Subsequent to Acquisition
Improvements	41,035
Gross Amount at which Carried
Land and Development Costs	0
Buildings & Improvements	143,553
Total	143,553
Accumulated Depreciation	44,713
250 West 57th Street, New York, NY | office/ retail
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	174,422
Initial Cost to the Company
Land and Development Costs	2,117
Building & Improvements	5,041
Cost Capitalized Subsequent to Acquisition
Improvements	168,501
Gross Amount at which Carried
Land and Development Costs	2,117
Buildings & Improvements	173,542
Total	175,659
Accumulated Depreciation	58,624
501 Seventh Avenue, New York, NY | office/ retail
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to the Company
Land and Development Costs	1,100
Building & Improvements	2,600
Cost Capitalized Subsequent to Acquisition
Improvements	99,073
Gross Amount at which Carried
Land and Development Costs	1,100
Buildings & Improvements	101,673
Total	102,773
Accumulated Depreciation	49,386
1359 Broadway, New York, NY | office/ retail
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to the Company
Land and Development Costs	1,233
Building & Improvements	1,809
Cost Capitalized Subsequent to Acquisition
Improvements	70,054
Gross Amount at which Carried
Land and Development Costs	1,233
Buildings & Improvements	71,863
Total	73,096
Accumulated Depreciation	35,619
350 Fifth Avenue (Empire State Building), New York, NY | office/ retail
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to the Company
Land and Development Costs	21,551
Building & Improvements	38,934
Cost Capitalized Subsequent to Acquisition
Improvements	983,452
Gross Amount at which Carried
Land and Development Costs	21,551
Buildings & Improvements	1,022,386
Total	1,043,937
Accumulated Depreciation	339,787
One Grand Central Place, New York, NY | office/ retail
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to the Company
Land and Development Costs	7,240
Building & Improvements	17,490
Cost Capitalized Subsequent to Acquisition
Improvements	289,760
Gross Amount at which Carried
Land and Development Costs	7,222
Buildings & Improvements	307,268
Total	314,490
Accumulated Depreciation	139,061
First Stamford Place, Stamford, CT | office
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	179,094
Initial Cost to the Company
Land and Development Costs	22,952
Building & Improvements	122,739
Cost Capitalized Subsequent to Acquisition
Improvements	75,313
Gross Amount at which Carried
Land and Development Costs	24,861
Buildings & Improvements	196,143
Total	221,004
Accumulated Depreciation	97,356
One Station Place, Stamford, CT (Metro Center) | office
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	84,931
Initial Cost to the Company
Land and Development Costs	5,313
Building & Improvements	28,602
Cost Capitalized Subsequent to Acquisition
Improvements	28,996
Gross Amount at which Carried
Land and Development Costs	5,313
Buildings & Improvements	57,598
Total	62,911
Accumulated Depreciation	34,344
383 Main Avenue, Norwalk, CT (1) | office
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	29,692
Initial Cost to the Company
Land and Development Costs	2,262
Building & Improvements	12,820
Cost Capitalized Subsequent to Acquisition
Improvements	6,582
Gross Amount at which Carried
Land and Development Costs	1,679
Buildings & Improvements	19,985
Total	21,664
Accumulated Depreciation	0
500 Mamaroneck Avenue, Harrison, NY | office
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to the Company
Land and Development Costs	4,571
Building & Improvements	25,915
Cost Capitalized Subsequent to Acquisition
Improvements	27,053
Gross Amount at which Carried
Land and Development Costs	4,571
Buildings & Improvements	52,968
Total	57,539
Accumulated Depreciation	28,856
10 Bank Street, White Plains, NY | office
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	30,719
Initial Cost to the Company
Land and Development Costs	5,612
Building & Improvements	31,803
Cost Capitalized Subsequent to Acquisition
Improvements	20,191
Gross Amount at which Carried
Land and Development Costs	5,612
Buildings & Improvements	51,994
Total	57,606
Accumulated Depreciation	26,841
10 Union Square, New York, NY | retail
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	49,486
Initial Cost to the Company
Land and Development Costs	5,003
Building & Improvements	12,866
Cost Capitalized Subsequent to Acquisition
Improvements	3,805
Gross Amount at which Carried
Land and Development Costs	5,003
Buildings & Improvements	16,671
Total	21,674
Accumulated Depreciation	9,121
1542 Third Avenue, New York, NY | retail
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	29,656
Initial Cost to the Company
Land and Development Costs	2,239
Building & Improvements	15,266
Cost Capitalized Subsequent to Acquisition
Improvements	473
Gross Amount at which Carried
Land and Development Costs	2,239
Buildings & Improvements	15,739
Total	17,978
Accumulated Depreciation	9,084
1010 Third Avenue, New York, NY and 77 West 55th Street, New York, NY | retail
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	36,250
Initial Cost to the Company
Land and Development Costs	4,462
Building & Improvements	15,819
Cost Capitalized Subsequent to Acquisition
Improvements	1,301
Gross Amount at which Carried
Land and Development Costs	4,462
Buildings & Improvements	17,120
Total	21,582
Accumulated Depreciation	9,984
69-97 Main Street, Westport, CT | retail
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to the Company
Land and Development Costs	2,782
Building & Improvements	15,766
Cost Capitalized Subsequent to Acquisition
Improvements	6,595
Gross Amount at which Carried
Land and Development Costs	2,782
Buildings & Improvements	22,361
Total	25,143
Accumulated Depreciation	8,740
103-107 Main Street, Westport, CT | retail
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to the Company
Land and Development Costs	1,243
Building & Improvements	7,043
Cost Capitalized Subsequent to Acquisition
Improvements	371
Gross Amount at which Carried
Land and Development Costs	1,260
Buildings & Improvements	7,397
Total	8,657
Accumulated Depreciation	2,968
345 E 94th Street NY (2) | Multifamily
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	49,421
Initial Cost to the Company
Land and Development Costs	44,228
Building & Improvements	55,766
Cost Capitalized Subsequent to Acquisition
Improvements	19
Gross Amount at which Carried
Land and Development Costs	44,228
Buildings & Improvements	55,785
Total	100,013
Accumulated Depreciation	0
Victory 561 10th Ave NY (2) | Multifamily
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	126,338
Initial Cost to the Company
Land and Development Costs	91,437
Building & Improvements	124,997
Cost Capitalized Subsequent to Acquisition
Improvements	28
Gross Amount at which Carried
Land and Development Costs	91,437
Buildings & Improvements	125,025
Total	216,462
Accumulated Depreciation	0
Property for development at the Transportation Hub in Stamford, CT | land
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Encumbrances	0
Initial Cost to the Company
Land and Development Costs	4,542
Building & Improvements	0
Cost Capitalized Subsequent to Acquisition
Improvements	8,132
Gross Amount at which Carried
Land and Development Costs	12,674
Buildings & Improvements	0
Total	12,674
Accumulated Depreciation	$ 0